Figure 6. Business category and data flow of power dispatching
In addition to control area and non-control area services, there is
management information zone for organization and management of
production and personnel. More services such as administrative telephone
network management, electric power enterprise data transmission are also
involved in such zone. These services of management information zone are
carried on enterprise data network.
3.2. Challenges of Electric Power Data Transmission
During the operation of power grid, the operating information of power
plant/station such as voltage, current, active power, reactive power,
circuit breaker opening/closing status is collected through various
sensors installed on primary equipment like lines, buses, circuit
breakers, transformers, generators, etc. Such information is used for
emergency control by local control devices such as relay protection and
safety automatic devices, and is also sent to dispatch master station
through dispatch data network channel.
The transmission of electric power data from a plant/station to dispatch
master station occurs in three ways: (1)some measurement data are
regularly sent to master station in real-time; (2) alarm information and
fault analysis results are sent directly after generation; (3)when the
master station summons monitoring signals and/or graphical model
information, the plant/station send data immediately. These data
transmission methods can be summarized as follows: when there is no
special data demand, data from plant/station are send to dispatch master
station periodically; when any plant/station or dispatch master station
triggers a data transmission event, such as the emergence of alarm
information in plant/station or data summon request from dispatch master
station, the plant/station would immediately send corresponding data to
the master station.
These data transmission methods are adopted because power grid has high
requirements on data transmission time delay performance. As a bridge
connecting power plants and load demands, any change in load side may
cause fluctuations in entire power grid’s operating status. Various
protection devices and automatic control equipment are used to enhance
the local stability of power grid. And in order to maintain the safe and
stable operation of power network, real-time monitoring of whole network
status by dispatch control center is necessary. Currently, power grid
lacks technical methods to judge the credibility of electric power data
and mainly relies on traditional hardware such as firewalls and
encryption isolation devices to guard against malicious attacks and data
tampering. As energy infrastructure, power grid security defense level
urgently needs to be further improved.
Applying blockchain technology to the field of electric power data
transmission will bring three advantages: first, it effectively enhances
the credibility of electric power data, laying foundation for the future
intelligent and digital development of power grid; second, it can
establish a reliable data traceability mechanism, providing a basis for
the analysis and judgment of various events; third, it would optimize
current power data organization, supporting data governance and
management for power enterprises.
4. Electric Power Data Transmission Based on Parallel Proof of Work
Algorithm
Although blockchain technology can effectively enhance data credibility
and traceability, the drawbacks of current consensus algorithms restrict
their applications in electric power data transmission.
This paper proposes a Parallel Proof of Work algorithm (P-PoW) based on
early blockchain consensus mechanism, for the sake of enhancing the
credibility and traceability of electric power data transmission.
4.1. Principle of Parallel Proof of Work Algorithm
The core idea of Parallel Proof of Work algorithm is to separate Proof
of Work calculation process from new block generation process. Figure 7
shows the schematic diagram of Parallel Proof of Work algorithm
principle. The blockchain structure shown is similar to Figure 1, where
each block is divided into a block header and block data area. For P-PoW
algorithm, block header contains P , which is a hash pointer to
previous block header. M stands for the Merkle root hash of
current block data. TS represents the timestamp at which moment
current block is generated. And S is the signature of P-PoW
algorithm. The subscript indices in Fig. 7 representing current block
order. In block data area, D is the electric power data written
into block, with two subscripts representing the position of data item
in block data area and the current block order, respectively.
Unlike PoW algorithm, P-PoW algorithm no longer iteratively calculates
block header to find a suitable random number nonce to generate a
new block. Instead, P-PoW algorithm extracts the hash pointer Pfrom block header and generates a signature S by iteratively
executing P-PoW algorithm. At the same time, to achieve real-time
transmission of electric power data, P-PoW algorithm has eliminated the
block generation target field in block header.